This invention is generally directed to an electrophotographic imaging device and more specifically a generating layer for use in overcoated photoreceptors, which generator acts as an adhesive and is capable of generating charges when a pigment is dispersed therein.
The formation and development of images on imaging surfaces of photoconductive materials by electrostatic means is well known, one of the most widely used processes being xerography which is described in U.S. Pat. No. 2,297,691. Many types of photoconductors have been developed over the years for use in such imaging methods, these photoconductors including well known organic materials, inorganic materials and mixtures thereof. Recently there has been developed overcoated photoreceptor materials which comprise a series of layered compositions which photoreceptors can be used in electrophotographic imaging systems to obtain higher quality images with the overcoating acting as a protection for the photoreceptor. The details of this type overcoated photoreceptor are fully disclosed in copending application U.S. Ser. No. 881,262, filed Feb. 24, 1978 on Electrophotographic Imaging Method, S. Tutihasi, and U.S. Ser. No. 905,250, filed May 12, 1978 on Dielectric Overcoated Photoresponse and Imaging Member and Imagining Method, J. Y. C. Chu, S. Tutihasi, the specification, working examples and drawings of these applications being totally incorporated herein by reference.
While these types of photoreceptors have many advantages, there continues to be a need for a more simplified type of organic photoreceptor which can be more easily prepared and which has greater mechanical stability. Also in the photoreceptors described in the copending applications identified above where the overcoating layer constitutes a preformed mechanically tough film, it may be necessary to provide sufficient adhesive material in order to provide an integral structure which can be useful in a repetitive imaging method. It would be desirable to eliminate the need for a separate adhesive layer as this would simplify the manufacture of an overcoated photoreceptor and would additionally improve the mechanical stability of such a photoreceptor. Further if such a layer can also be made to function as a generating material while at the same time being compatible with other materials used in the system, there would be provided an improved overcoated photoreceptor which could be used over long periods of time without materially adversely affecting the quality of the image produced with such a photoreceptor. Thus, for example, should there be insufficient adhesion of the generating layer to the transport layer beneath it and the overcoating layer above it, separation and peeling can occur which will result in low quality images over a period of time when using a photoreceptor containing such layers.
Overcoated photoreceptor devices such as described in U.S. Pat. No. 3,041,167 and in the copending applications mentioned hereinbefore, as well as the improved photoreceptor of the present invention, which will be discussed in detail hereinafter, can be used in a number of imaging systems. In one preferred method of operation as described in the copending applications mentioned above the photoconductor member is charged a first time with electrostatic charges of negative charge polarity, subsequently charged a second time with electrostatic charges of a positive polarity for the purpose of substantially neutralizing the charges residing on the electrically insulating surface of the member, and subsequently exposing the member to an imagewise pattern of activating electromagnetic radiation thereby forming an electrostatic latent image. The image can then be developed to form a visible image which is transferred to a receiving member. The photoreceptor imaging member used may be subsequently reused to form additional reproductions after the erase and cleaning steps are accomplished. Other imaging methods in which overcoated photoreceptors can be used are described by Mark in an article appearing in Photographic Science and Engineering, Volumne 18, No. 3, Pages 254-261, May/June 1974.